services: Add pam-mount-volume-service-type.

The `pam-mount-volumes-service-type' adds additional volumes to the
pam-mount-service-type in addition to any that are already specified in
`pam-mount-rules'.

* doc/guix.texi (PAM Mount Volume Service): add documentation for
`pam-mount-service-type'.
* gnu/services/pam-mount.scm: new file.
* Makefile.am: add pam-mount tests
* tests/services/pam-mount.scm: new tests

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

4 files changed, 296 insertions, 1 deletions

diff --git a/Makefile.am b/Makefile.am
index ca9ec48fa3..693e14effe 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -559,6 +559,7 @@ SCM_TESTS =					\
   tests/services/configuration.scm		\
   tests/services/lightdm.scm			\
   tests/services/linux.scm			\
+  tests/services/pam-mount.scm			\
   tests/services/telephony.scm			\
   tests/services/vpn.scm			\
   tests/sets.scm				\
diff --git a/doc/guix.texi b/doc/guix.texi
index 65ca18a1be..71f9f29169 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -116,6 +116,7 @@ Copyright @copyright{} 2022 Antero Mejr@*
 Copyright @copyright{} 2023 Karl Hallsby@*
 Copyright @copyright{} 2023 Nathaniel Nicandro@*
 Copyright @copyright{} 2023 Tanguy Le Carrour@*
+Copyright @copyright{} 2023 Brian Cully@*
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -37927,6 +37928,104 @@ The complete list of possible options can be found in the man page for
 @end table
 @end deftp
 
+@subheading PAM Mount Volume Service
+@cindex pam volume mounting
+
+PAM mount volumes are automatically mounted at login by the PAM login
+service according to a set of per-volume rules.  Because they are
+mounted by PAM the password entered during login may be used directly to
+mount authenticated volumes, such as @code{cifs}, using the same
+credentials.
+
+These volumes will be added in addition to any volumes directly
+specified in @code{pam-mount-rules}.
+
+Here is an example of a rule which will mount a remote CIFS share from
+@file{//remote-server/share} into a sub-directory of @file{/shares}
+named after the user logging in:
+
+@lisp
+(simple-service 'pam-mount-remote-share pam-mount-volume-service-type
+                (list (pam-mount-volume
+                       (secondary-group "users")
+                       (file-system-type "cifs")
+                       (server "remote-server")
+                       (file-name "share")
+                       (mount-point "/shares/%(USER)")
+                       (options "nosuid,nodev,seal,cifsacl"))))
+@end lisp
+
+@deftp {Data Type} pam-mount-volume-service-type
+Configuration for a single volume to be mounted.  Any fields not
+specified will be omitted from the run-time PAM configuration.  See
+@uref{http://pam-mount.sourceforge.net/pam_mount.conf.5.html,
+the man page} for the default values when unspecified.
+
+@table @asis
+@item @code{user-name} (type: maybe-string)
+Mount the volume for the given user.
+
+@item @code{user-id} (type: maybe-integer-or-range)
+Mount the volume for the user with this ID.  This field may also be
+specified as a pair of @code{(start . end)} indicating a range of user
+IDs for whom to mount the volume.
+
+@item @code{primary-group} (type: maybe-string)
+Mount the volume for users with this primary group name.
+
+@item @code{group-id} (type: maybe-integer-or-range)
+Mount the volume for the users with this primary group ID.  This field
+may also be specified as a cons cell of @code{(start . end)} indicating
+a range of group ids for whom to mount the volume.
+
+@item @code{secondary-group} (type: maybe-string)
+Mount the volume for users who are members of this group as either a
+primary or secondary group.
+
+@item @code{file-system-type} (type: maybe-string)
+The file system type for the volume being mounted (e.g., @code{cifs})
+
+@item @code{no-mount-as-root?} (type: maybe-boolean)
+Whether or not to mount the volume with root privileges.  This is
+normally disabled, but may be enabled for mounts of type @code{fuse}, or
+other user-level mounts.
+
+@item @code{server} (type: maybe-string)
+The name of the remote server to mount the volume from, when necessary.
+
+@item @code{file-name} (type: maybe-string)
+The location of the volume, either local or remote, depending on the
+@code{file-system-type}.
+
+@item @code{mount-point} (type: maybe-string)
+Where to mount the volume in the local file-system.  This may be set to
+@file{~} to indicate the home directory of the user logging in.  If this
+field is omitted then @file{/etc/fstab} is consulted for the mount
+destination.
+
+@item @code{options} (type: maybe-string)
+The options to be passed as-is to the underlying mount program.
+
+@item @code{ssh?} (type: maybe-boolean)
+Enable this option to pass the login password to SSH for use with mounts
+involving SSH (e.g., @code{sshfs}).
+
+@item @code{cipher} (type: maybe-string)
+Cryptsetup cipher name for the volume.  To be used with the @code{crypt}
+@code{file-system-type}.
+
+@item @code{file-system-key-cipher} (type: maybe-string)
+Cipher name used by the target volume.
+
+@item @code{file-system-key-hash} (type: maybe-string)
+SSL hash name used by the target volume.
+
+@item @code{file-system-key-file-name} (type: maybe-string)
+File name of the file system key for the target volume.
+
+@end table
+@end deftp
+
 
 @node Guix Services
 @subsection Guix Services
diff --git a/gnu/services/pam-mount.scm b/gnu/services/pam-mount.scm
index 21c34ddd61..dbb9d0285f 100644
--- a/gnu/services/pam-mount.scm
+++ b/gnu/services/pam-mount.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2019 Guillaume Le Vaillant <glv@posteo.net>
+;;; Copyright © 2023 Brian Cully <bjc@spork.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -23,9 +24,15 @@
   #:use-module (gnu system pam)
   #:use-module (guix gexp)
   #:use-module (guix records)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
   #:export (pam-mount-configuration
             pam-mount-configuration?
-            pam-mount-service-type))
+            pam-mount-service-type
+
+            pam-mount-volume
+            pam-mount-volume?
+            pam-mount-volume-service-type))
 
 (define %pam-mount-default-configuration
   `((debug (@ (enable "0")))
@@ -102,6 +109,11 @@
                              (list optional-pam-mount))))
            pam))))))
 
+(define (extend-pam-mount-configuration initial extensions)
+  "Extends INITIAL with EXTENSIONS."
+  (pam-mount-configuration (rules (append (pam-mount-configuration-rules
+                                           initial) extensions))))
+
 (define pam-mount-service-type
   (service-type
    (name 'pam-mount)
@@ -109,6 +121,106 @@
                                         pam-mount-etc-service)
                      (service-extension pam-root-service-type
                                         pam-mount-pam-service)))
+   (compose concatenate)
+   (extend extend-pam-mount-configuration)
    (default-value (pam-mount-configuration))
    (description "Activate PAM-Mount support.  It allows mounting volumes for
 specific users when they log in.")))
+
+(define (field-name->tag field-name)
+  "Convert FIELD-NAME to its tag used by the configuration XML."
+  (match field-name
+    ('user-name 'user)
+    ('user-id 'uid)
+    ('primary-group 'pgrp)
+    ('group-id 'gid)
+    ('secondary-group 'sgrp)
+    ('file-system-type 'fstype)
+    ('no-mount-as-root? 'noroot)
+    ('file-name 'path)
+    ('mount-point 'mountpoint)
+    ('ssh? 'ssh)
+    ('file-system-key-cipher 'fskeycipher)
+    ('file-system-key-hash 'fskeyhash)
+    ('file-system-key-file-name 'fskeypath)
+    (_ field-name)))
+
+(define-maybe string)
+
+(define (serialize-string field-name value)
+  (list (field-name->tag field-name) value))
+
+(define (integer-or-range? value)
+  (match value
+    ((start . end) (and (integer? start)
+                        (integer? end)))
+    (_ (number? value))))
+
+(define-maybe integer-or-range)
+
+(define (serialize-integer-or-range field-name value)
+  (let ((value-string (match value
+                        ((start . end) (format #f "~a-~a" start end))
+                        (_ (number->string value)))))
+    (list (field-name->tag field-name) value-string)))
+
+(define-maybe boolean)
+
+(define (serialize-boolean field-name value)
+  (let ((value-string (if value "1" "0")))
+    (list (field-name->tag field-name) value-string)))
+
+(define-configuration pam-mount-volume
+  (user-name maybe-string "User name to match.")
+  (user-id maybe-integer-or-range
+   "User ID, or range of user IDs, in the form of @code{(start . end)} to\nmatch.")
+  (primary-group maybe-string "Primary group name to match.")
+  (group-id maybe-integer-or-range
+   "Group ID, or range of group IDs, in the form of @code{(start . end)} to\nmatch.")
+  (secondary-group maybe-string
+   "Match users who belong to this group name as either a primary or secondary\ngroup.")
+  (file-system-type maybe-string "File system type of volume being mounted.")
+  (no-mount-as-root? maybe-boolean
+                     "Do not use super user privileges to mount this volume.")
+  (server maybe-string "Remote server this volume resides on.")
+  (file-name maybe-string "Location of the volume to be mounted.")
+  (mount-point maybe-string
+               "Where to mount the volume in the local file system.")
+  (options maybe-string "Options to pass to the underlying mount program.")
+  (ssh? maybe-boolean "Whether to pass the login password to SSH.")
+  (cipher maybe-string "Cryptsetup cipher named used by volume.")
+  (file-system-key-cipher maybe-string
+                          "Cipher name used by the target volume.")
+  (file-system-key-hash maybe-string
+                        "SSL hash name used by the target volume.")
+  (file-system-key-file-name maybe-string
+   "File name for the file system key used by the target volume."))
+
+(define (pam-mount-volume->sxml volume)
+  ;; Convert a list of configuration fields into an SXML-compatible attribute
+  ;; list.
+  (define xml-attrs
+    (filter-map (lambda (field)
+                  (let* ((accessor (configuration-field-getter field))
+                         (value (accessor volume)))
+                    (and (not (eq? value %unset-value))
+                         (list (field-name->tag (configuration-field-name
+                                                 field)) value))))
+                pam-mount-volume-fields))
+
+  `(volume (@ ,@xml-attrs)))
+
+(define (pam-mount-volume-rules volumes)
+  (map pam-mount-volume->sxml volumes))
+
+(define pam-mount-volume-service-type
+  (service-type (name 'pam-mount-volume)
+                (extensions (list (service-extension pam-mount-service-type
+                                                     pam-mount-volume-rules)))
+                (compose concatenate)
+                (extend append)
+                (default-value '())
+                (description
+                 "Mount remote volumes such as CIFS shares @i{via}
+@acronym{PAM, Pluggable Authentication Modules} when logging in, using login
+credentials.")))
diff --git a/tests/services/pam-mount.scm b/tests/services/pam-mount.scm
new file mode 100644
index 0000000000..bfbd15967f
--- /dev/null
+++ b/tests/services/pam-mount.scm
@@ -0,0 +1,83 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2023 Brian Cully <bjc@spork.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (tests services pam-mount)
+  #:use-module (gnu services pam-mount)
+  #:use-module (gnu system pam)
+  #:use-module (gnu services)
+  #:use-module (gnu services configuration)
+  #:use-module (guix derivations)
+  #:use-module (guix gexp)
+  #:use-module (guix grafts)
+  #:use-module (guix store)
+  #:use-module (guix tests)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-64))
+
+(define pam-mount-volume-fields (@@ (gnu services pam-mount)
+                                    pam-mount-volume-fields))
+(define field-name->tag (@@ (gnu services pam-mount)
+                            field-name->tag))
+
+(define pam-mount-volume->sxml (@@ (gnu services pam-mount)
+                                   pam-mount-volume->sxml))
+
+(test-begin "services-pam-mount")
+
+(test-group "field-name->tag"
+  (let ((field-map '((user-name user)
+                     (user-id uid)
+                     (primary-group pgrp)
+                     (group-id gid)
+                     (secondary-group sgrp)
+                     (file-system-type fstype)
+                     (no-mount-as-root? noroot)
+                     (server server)
+                     (file-name path)
+                     (mount-point mountpoint)
+                     (options options)
+                     (ssh? ssh)
+                     (cipher cipher)
+                     (file-system-key-cipher fskeycipher)
+                     (file-system-key-hash fskeyhash)
+                     (file-system-key-file-name fskeypath))))
+
+    (test-equal "all fields accounted for"
+      (map car field-map)
+      (map configuration-field-name pam-mount-volume-fields))
+
+    (for-each (match-lambda
+                ((field-name tag-name)
+                 (test-eq (format #f "~a -> ~a" field-name tag-name)
+                   (field-name->tag field-name) tag-name)))
+              field-map)))
+
+(let ((tmpfs-volume (pam-mount-volume
+                     (secondary-group "users")
+                     (file-system-type "tmpfs")
+                     (mount-point "/run/user/%(USERUID)")
+                     (options "someoptions"))))
+  (test-equal "tmpfs"
+    '(volume (@ (sgrp "users")
+                (fstype "tmpfs")
+                (mountpoint "/run/user/%(USERUID)")
+                (options "someoptions")))
+    (pam-mount-volume->sxml tmpfs-volume)))
+
+(test-end "services-pam-mount")